The present invention relates to the field of serial bus interfaces, and more particularly to connecting peripherals to a host computer system through serial buses.
In today""s homes, the personal computer (PC) and consumer electronics are beginning to merge into an xe2x80x9centertainment PC.xe2x80x9d The entertainment PC is projected to connect consumer electronic products such as DBS (Direct Broadcast Satellite), HDTV (High-definition Television), and DVD (Digital Versatile Disk), among others, to a PC. However, the conventional PC faces several problems in accommodating both the PC peripherals and consumer electronics products due to its configuration and expandability limitations.
Basically, a conventional PC is configured as a box containing major system components such as the processor, system bus, RAM (Random Access Memory), storage unit such as a hard disk drive, and graphics card, etc. A user generally interacts with the PC through input/output (I/O) devices such as a monitor, a keyboard, and a mouse, which are connected to the box through various cables. Hence for the most part, the user sees and interacts with the I/O devices of a PC.
However, the industry is presently moving toward a reduced and sealed PC box configuration, which can be stored in an inconspicuous place in the home. The sealed PC box contains components that users do not come m direct contact with, such as a processor, system bus, storage units, and graphics cards. The parts or components that a user physically interacts with such as I/O devices are assembled as a work- or play-station in convenient places such as a living room or a home-office. These components include I/O devices such as display monitors, keyboard, and mouse. These devices are connected to a remote box containing, for example, a floppy drive or a DVD player, to enable direct access for users. The remote box provides connection to the sealed PC box through one or more cables and may be placed under a display monitor.
The implementation of such an evolutionary entertainment PC in the home is limited in the way a conventional PC is attached to various external devices through a myriad of cables. For example, a typical PC may be connected to devices such as a monitor, keyboard, mouse, printer, modem, microphone, speakers, videocam, CD-ROM (Compact Disk-Read Only Memory), and DVD, etc. All these devices usually require separate cables. Indeed, connecting such devices to a PC over any appreciable distance is a formidable, complicated and messy task.
Another major limitation involves the allocation of interrupts in adding a peripheral device to the PC. Specifically, adding a component or device to a conventional PC box can be a difficult process due to the finite number of interrupts available. Moreover, because an ISA (Industry Standard Architecture) bus does not reliably share interrupts between various devices, the interrupt or IRQ conflicts are very common for devices that attach to the ISA bus. Accordingly, the conventional PC does not provide an easy and technologically sound framework upon which to build an entertainment PC.
To overcome the limitations of conventional PCs, two standards have been proposed and adopted by the industry to a large degree. First, an IEEE 1394 serial bus, commonly referred to as xe2x80x9cFireWire,xe2x80x9d was proposed and adopted as an industry standard to replace various cables connecting myriad of components or peripherals to the PC box. A key advantage of this bus is its ability to connect both consumer electronics equipment and PC components. The 1394 cable carries both data and power: it contains two twisted pairs of wires for carrying data signals and two additional wires for power. Further, it can connect two components up to about 10 meters apart without a repeat assignment. Moreover, it allows daisy chain connection of components. The 1394 wire comes in two versions, a and b, and starts at 400 Mb/s (megabits per second) to 1 to 1.6 Gb/s (gigabits per second). Due to its high transmission rate, the IEEE 1394 bus is projected to be the standard cable to connect high speed drives that are connected by parallel cables such as IDEs and SCSIs (Small Computer System Interface).
Second, a Universal Serial Bus (USB) was adopted as an industry standard to replace I/O connections to conventional PCs. The USB eliminates IRQ conflicts and allows up to 127 devices to be attached to a PC. USB allows data transmission rate of 1.5 to 25 Mb/s and targets devices such as keyboard, mouse, etc. which typically require low bandwidth. Intel, the originator of USB, is rapidly incorporating a USB interface into its system logic chip sets and is including two USB connectors on its motherboards.
The adoption of the IEEE 1394 bus and USB provides an added momentum to the implementation of entertainment PC. However, in order to maximize the benefits of these buses, the conventional PC is projected to be modified to facilitate the connections between consumer electronics products and PC components. The reconfiguration of a PC involves repartitioning the PC system by making the PC look and feel more like a consumer electronics product to a user. This reconfiguration of a PC is based, in part, on an industry initiative concept called xe2x80x9cdevice bay,xe2x80x9d which is essentially a way of connecting components or peripherals to a sealed PC. A device bay is classified according to the location of a peripheral. A local device bay refers to plugging a peripheral into a slot in the sealed box. On the other hand, a remote device bay refers to connecting a peripheral device at a physically different location through cables.
Unfortunately, a remote device bay requires both IEEE 1394 and USB cables to connect a remote peripheral device to an entertainment PC. This is because a USB cable can not connect consumer electronics products to a PC. It can only connect PC peripherals. On the other hand, the IEEE 1394 cable connects the entertainment PC to consumer electronics products.
Furthermore, one of the main benefits of an entertainment PC is its capacity to deliver digital videos to the living room. High quality consumer electronic products such as DBS, HDTV (High-definition television), and DVD, are making digital video a reality. Transmission of high resolution digital video data streams, however, presents a problem on a large display screen even on an IEEE 1394 bus. For example, to display digital video data at 16 bit YUV with a resolution of 1920xc3x971080 at 30 frames per second requires 995 Mb/s (megabits per second) which exceeds the lower end bandwidth of 400 Mb/s supported by the IEEE 1394 bus. However, IEEE 1394 bus may be able to handle such video display at the higher bandwidth (1 to 1.6 Gb/s) it supports.
Thus,what is needed is an apparatus and method for transparently bridging USB over IEEE 1394 bus so that only one cable is needed to connect components of the entertainment PC located in different parts of a home. In addition, what is further needed is an apparatus for transparently delivering video data streams over IEEE 1394 bus.
The present invention provides a transparent USB-to-1394 bridge function whereby USB data packets are reformatted for transmission over an IEEE 1394 bus. The present invention also provides delivery of video data streams transparently from the host graphics card to a peripheral device over the IEEE 1394 bus.
In the present invention, a host computer system is coupled to a remote peripheral device through a single IEEE 1394 bus. The host system includes a processor, a bus, a memory, a graphics card, and a host interface circuit for interfacing the host system with the remote peripheral device. A remote interface circuit residing within the remote peripheral device provides an interface with the host system. The host interface circuit and the remote interface circuit are connected to each other by the single 1394 bus cable. Both the host interface circuit and the remote interface circuit provide USB-to-1394 bridging functions. Hence, USB devices as well as IEEE 1394 devices coupled to either the host system or the remote peripheral device can communicate over the single 1394 cable, thereby eliminating the need for any additional interconnect cables extending between the host and peripheral device.
In another embodiment, the present invention provides a graphics interface circuit in the host interface circuit. The graphics interface circuit provides an interface to a graphics controller in the host system for receiving and transmitting video data streams over 1394 bus to remote peripherals. The present invention also provides a compression engine in the graphics interface circuit to compress video data streams for delivery in the computer system over the IEEE 1394 bus.